Beyond Seismic and Logs: Real-Time Geological Model Updates from UDAR-Based Inversions

Abstract Field development in thin, heterogeneous reservoirs presents persistent challenges due to geological complexities such as pinch-outs, shale interbeds, and abrupt changes in structural dip. These features are often below seismic resolution and difficult to capture using traditional 1D petrophysical logs alone. Consequently, predicting lateral reservoir continuity and sand geometry with sufficient confidence remains a significant uncertainty in well planning and reservoir modeling. Ultra-Deep Azimuthal Resistivity (UDAR) inversion provides a transformative solution by enabling high-resolution structural and stratigraphic interpretation around the wellbore. This study explores the integration of UDAR inversion data to update geological facies models and improve reservoir characterization. UDAR's 2D and 3D inversion products, derived from advanced reservoir mapping while drilling (RMWD), offer insight into resistivity-based geo-bodies that indicate the presence and distribution of sand. These interpretations, when integrated with borehole image logs and traditional LWD measurements, support the development of more geologically realistic models in near real-time. To demonstrate the value of this approach, a blind well test was performed using two sector models. The first was built using vertical/semi-vertical legacy well data only, while the second incorporated both vertical/semi-vertical wells and UDAR-derived sand body interpretations from multiple horizontal wells in the area. The second model showed a significantly improved match to the blind well's actual log responses, validating the contribution of UDAR interpretation in reducing geological uncertainty. By capturing sub-seismic scale depositional features and delivering 360-degree structural updates around the wellbore, UDAR-based resistivity inversions enhance the spatial resolution of facies architecture. This approach revealed key depositional trends and stratigraphic variations across the study area, which are critical for optimizing reservoir performance and well placement. The results underscore that 1D solutions are no longer sufficient in complex field environments. Integrating multi-dimensional UDAR inversion data into the geological modeling workflow provides a more reliable foundation for reserves estimation and strategic field development, ultimately enabling more informed decisions in both near-field and full-field development planning.